A curling stone slides across the ice at 2.0 m/s. The energy in its kinetic store is 40 J. What is the mass of the stone?
10 kg10\ \mathrm{kg}10 kg
5.0 kg5.0\ \mathrm{kg}5.0 kg
40 kg40\ \mathrm{kg}40 kg
20 kg20\ \mathrm{kg}20 kg